This invention relates generally to electrical contact springs used in electro-mechanical horological devices of the type having an oscillating balance wheel driven by a miniature electric coil and magnet system. Examples of such watches are seen in U.S. Pat. No. 3,140,376 issued July 7, 1964 to W. Tilse et al or U.S. Pat. No. 3,699,762 issued Oct. 24, 1972 to Zatsky.
The simplest type of contact spring is a flat spring which is wiped in alternate directions by an electrically conductive pin on the balance wheel as is shown in U.S. Pat. No. 3,529,415 issued Sept. 22, 1970 to Wuthrich or U.S. Pat. No. 3,698,179 issued Oct. 17, 1972 to Kaulins. However a flat spring does not provide the best electrical contact or self-cleaning action. Another type of contact spring is a round cross section spring wire which provides good cleaning action, but which is stiff and interferes with proper operation of the balance wheel. Other constructions have been suggested in the prior art for forming the ends or controlling the contact area on the ends of the contact spring, but these are expensive due to the extremely small dimensions of the contact spring which is, for example, on the order of 71/2 millimeters long, 0.15 millimeters wide and 0.025 millimeters thick. Examples of the aforementioned prior art shown in the drawings.
Accordingly, one object of the present invention is to provide an improved construction for a contact spring for an electro-mechanical watch which is inexpensive, and flexible while providing proper electrical contact and self-cleaning action.
Another object of the invention is to provide a less expensive and more effective construction for a contact spring in an electric watch.